Can the International Space Station Survive Until 2020?

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The International Space Station is undergoing an engineering
analysis and risk assessment to gauge its ability to keep
operating until 2020 and beyond.

President Barack Obama’s National Space Policy, released in June
2010, called for, among other things, the continued operation of
the International
Space Station (ISS) by NASA in cooperation with its
international partners, "likely to 2020 or beyond."

"The good news is, so far, we haven’t found any showstoppers,"
said Brad Cothran, Boeing’s vehicle director for ISS.

"Our plan has been to get back to the ISS program and clear the
station to get to 2020," Cothran told SPACE.com. "After we get to
that point, we’ll enter what we call our phase three, and we’re
going to clear the ISS for
2028 and beyond," he said.

As NASA's prime contractor for the ISS, Boeing is responsible for
design, development, construction and integration of the orbiting
lab. The firm also assists NASA in operating the
space station. Boeing built all of the major U.S. elements
and is responsible for integrating the systems, procedures and
components of participating countries in the worldwide
enterprise.

Cothran said there are several categories defined to pull
together an overall, integrated health check of the ISS, from a
primary structure standing. The categories are: issues that could
cause catastrophic failures; function availability; and how the
shelf life of items can impact the ISS’ sustainability.

"We’ve spent many years of analyzing all the primary structures,"
specifically the dynamic loads the ISS experiences as it circuits
the Earth, Cothran said.

"One of the key interfaces that we were worried about is all
those modules hanging off the ISS truss. From a structural
standpoint, that interface is critical, and the good news is that
we have cleared that area and the attach points," Cothran said.

Russia’s Zarya
FGB, the first ISS module that was launched into orbit back
in November 1998, has been cleared to at least 2020, Cothran
said. That first-up hardware was U.S.-bankrolled, built by the
Khrunichev State Research and Production Space Center in Moscow
under a subcontract to The Boeing Co. for NASA.

Green-lighting the lines

As far as what could cause a catastrophic failure, Cothran said
that the analysis zeroed in on the space station’s high-pressure
oxygen lines. "They were one of the biggest worries," he said.

"We looked at pressures today and the number of cycles those
lines have been through," Cothran said, adding that a team
green-lighted the lines for a much longer life than they were
originally designed for.

In the area of functional ability, it turns out that the ISS'
solar arrays are degrading at a faster rate than originally
planned — between 1 and 2 percent per year rather than 1 percent.

"We’re seeing a very linear degradation across the entire fleet"
of solar arrays, Cothran said.

But why this is happening remains a mystery. It’s not yet
confirmed, but one data point from a satellite
in an ISS-like orbit and similar altitude suggests that the
proton and neutron environment is more severe than thought,
Cothran said.

The good news is that the issue shouldn't affect the orbiting
lab's operations for some time to come.

"We’re not going to run out of power until well past 10 years
from now," Cothran said. "It’s going to be somewhere within 2028,
plus or minus five years."

Ideally, by spotting this as an early issue, solutions like
making electronics more efficient, reducing power consumption or
putting some additional generation capability on the ISS can be
considered, Cothran said.

Replacing an entire solar array "is a very big deal and something
we don’t want to go do," he added.

Electronic memory loss

Yet another finding concerns the shelf life of memory devices
within electronics.

Surprisingly, the ISS is suffering from a case of electronic
memory loss. Erasable, programmable read-only memory devices —
also known as "e-proms" — do not hold their charge after about 10
years.

"They lose their state of internal charge….their internal memory.
It’s an interesting find that we’ve run across. So we’ve got a
plan now to go refresh those memory devices," Cothran said. That
adds up to redesign of computers to be more efficient, as well as
to get rid of obsolescence, he said.

Another lesson learned in building and running the ISS is
the role of lubricants.

"We were very against grease-based lubricants external in the
vacuum environment," Cothran said.

"Nobody had any data early on about grease in a vacuum
environment for an extended period of time. So everybody was
against it from a material standpoint," Cothran said. That has
come back to bite the ISS program somewhat, but fixes are on the
horizon, he added.

Debris trail

While there has long been concern about space junk
potentially damaging the ISS, researchers have also found that
the orbiting complex is subject to be dinged by its own detritus.

"It turns out there’s not as many big things out there as we had
once statistically forecasted. But we are seeing smaller
particles," Cothran said. A lot of those particles are
self-generated by the ISS. [ The
Worst Space Debris Events of All Time ]

"We are shedding in orbit … mostly paints, coatings," with the
thermal coating as the most prevalent, Cothran said. "As we come
back around [in Earth orbit] the next time or two or three or
four weeks later, whatever, we’re hitting our own debris trail."

Mars bound?

The Boeing assessment is not quite complete. But it's already
apparent that the ISS has been quite an engineering success,
Cothran said.

"The station has been remarkable if you look at how it’s flying
today and the number of failures we’ve had," he said. "It’s
totally surpassed any design requirements."

Many lessons were learned in the building, operation and
maintenance of the ISS.

"It’s an incredible facility," Cothran said. "We learned how to
put things together in space on ISS."

He said those lessons can be applied toward establishing a crewed
facility in the Earth-moon system, or toward the assembly of a
spaceship that would take astronauts to
Mars.

"The nation and NASA are very fortunate that it has been the kind
of station that it has been," Cothran said.

Leonard David has been reporting on the space industry for
more than five decades. He is former director of research for the
National Commission on Space and is co-author of Buzz Aldrin's
new book "Mission to Mars – My Vision for Space Exploration"
published by National Geographic. Follow us@Spacedotcom,Facebook orGoogle+.
Originally published on SPACE.com.